1. Field of the Invention
The present invention relates generally to medical devices and procedures that use catheters, or similar devices. More particularly, the present invention relates to a peelable sheath having a hub connector useable with such catheters or other devices. The invention has particular utility in percutaneous medical procedures. However, the present invention also may be found to have utility in other medical procedures or applications.
2. Description of the Prior Art
Sheaths for medical procedures are well known, particularly in percutaneous medical procedures. Generally, percutaneous medical devices, such as catheters, guide wires, or the like, are introduced into a body channel, such as a vein or artery, e.g. the femoral artery, through a sheath.
A sheath generally includes a slender, flexible tube arranged for insertion into the body channel to maintain an opening which allows communication with such channel. After insertion of the sheath, but before insertion of a catheter, it may be desirable to introduce fluids, such as a heparin flush, into the body channel. Therefore, it is desirable to provide structure for attaching the proximal end of the sheath to an external device, such as a pump or syringe.
It also may be desireable to provide structure for attaching the proximal end of the sheath to a dilator (e.g., to lock the sheath-dilator set together as one unit) or to the catheter passing through it (e.g., to prevent bleeding). In addition, it often is found to be advantageous, after the catheter has been fully inserted and manipulated into position, to remove the sheath, leaving only the catheter resident in the body channel. The present invention accommodates all these needs.
Of course, any device resident in a vein or artery reduces the volume of blood that can pass. Since a sheath is of larger diameter than the catheter passing through it, leaving the sheath resident in the vein or artery reduces the blood flow more than if only the smaller catheter is left resident therein. Accordingly, it may be desireable to remove the sheath and leave the catheter resident in the artery or vein. Unfortunately, conventional sheaths have a drawback in that typically they cannot be withdrawn after insertion of a catheter or other device. Most catheters terminate in enlarged hubs which prevent conventional sheaths from sliding off over the end. The sheath, therefore, must remain resident in the vein or artery throughout the procedure.
Peelable sheaths also are known. Generally, peelable sheaths permit removal of the sheath after insertion because it is not necessary for them to pass over the hub of the catheter. For example, U.S. Reissue Pat. No. No. 31,855 (Osborne) relates to a flexible cannula or sheath comprising material that readily tears in a longitudinal direction. The cannula is provided at its proximal end with a pair of open ended slits forming first and second tabs on opposite sides of the cannula. When the tabs are pulled apart, the cannula structure tears longitudinally along its length. Accordingly, the sheath can be removed by pulling the tabs apart after the catheter or other device has been inserted into the body.
U.S. Pat. Nos. 4,411,654 (Boarini) and 4,412,832 (Kling) each relate to a peelable introducer catheter or sheath also comprising a pair of open ended slits for facilitating tearing of the sheath along its longitudinal axis. Each of the Boarini and Kling patents further comprises a slidable sleeve, telescopically disposed at the proximal end of the sheath, for preventing premature tearing or disruption of the sheath, e.g. during insertion or manipulation.
U.S. Pat. No. 4,345,606 (Littleford) relates to a sleeve and introducer set in which the sleeve or sheath is partially split to facilitate removal. The introducer has a tapered end adapted to extend into a patient's body. The sleeve, formed of a hollow tube, has a first portion with an inner dimension greater than the outer dimension of the introducer and a second portion at the distal end of the sleeve which extends parallel to the introducer and in close engagement therewith. A gradual taper extends along the sleeve between the first and second portions. The sleeve has a longitudinal slit along the first portion, through the taper and terminating short of its forward extremity to permit the sleeve to be peeled away from, e.g., a pacemaker electrode after introduction. The slit, or severing means, comprises a plurality of "perforations" to form a weakened line along the length of the sleeve. Alternatively, the Littleford patent suggests the severing means may take the form of holes, through cuts, reduced wall thickness, or integral cutting agents, such as strings and the like.
In one embodiment of the Littleford patent, the introducer and sleeve also include corresponding hub and flange arrangements that provide a means for locking the two elements together, to prevent inadvertent motion of the sleeve with respect to the introducer as the two elements are being inserted into the patient. The sleeve includes a slit extending through the flange, along the first portion and through the taper, and terminating in the second portion.
Peelable sheaths provide advantages over prior sheaths. For example, as noted above, peelable sheaths can be withdrawn after insertion even if a catheter inserted therethrough has an enlarged hub. However, known peelable sheaths also have drawbacks. Peelable sheaths are more flexible than their predecessors and, thus, are not as responsive to manipulation, e.g., during insertion. This is particularly true for peelable sheaths having tabs preformed by open ended slits, such as described in the Boarini and Kling patents, because once the tabs are formed, the sheath loses much of its structural integrity.
The split sleeve introducer disclosed in the Littleford patent is an improvement over such prior sheaths in that it employs a flange structure. This flanged sheath generally is more responsive because the structural integrity of the sheath flange is more easily maintained until it is desired to peel away the sheath. The flange of the Littleford patent also provides an advantage in that the user can cap the flange with a finger or thumb, e.g., to reduce or prevent undesirable aspiration of the blood when the sheath is manipulated. However, since the slit extends through the flange of the Littleford device, it still is susceptible to premature splitting, e.g., by manipulation during insertion.
In addition, none of the split sheaths in these references are configured with a hub that is designed for attachment to an external device, such as a pump or syringe, as well as to a dilator or a catheter.